In terms of documents having a relation with the object of the invention we can consider U.S. Pat. No. 5,083,039 which describes a machine with stator control in which the stator of that machine is connected to a converter, said converter being capable of injecting into the electrical network with the demanded power factor.
Also, patent EP 1508951 A1 describes a system and a method by which a set of generators generates the active and reactive power demanded by a control system, with each generator demand values being generated bearing in mind its voltage limits and the electrical generator thermal capacity. The network side converters in that system can also generate reactive power
Dimitrius Arsudis Ph.D. thesis, “Doppeltgespeister Drehstromgenerator mit Spannungszwischenkreis-Umrichter im Rotorkreis für Windkraftanlagen”, describes a doubly fed induction machine control method by which the demanded amount of reactive power is generated in the stator of the machine by controlling the rotor currents in an appropriate manner.